/*
 * $AIST_Release: 0.9.0 $
 * Copyright 2011 Information Technology Research Institute, National
 * Institute of Advanced Industrial Science and Technology
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *    http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package aggr

import Aggregators._
import SerializedTypes._
import Util._

/**
 * "sample" aggregator.
 */
class Sample(nSamples: Long) extends Aggregator {

  override def aggregate(data: TraversableOnce[(Any, Any)])(writer: (Any, Any) => Unit): Unit = {
    require(nSamples > 0)
    // TODO: 可能ならリストにせずに処理したい

    val d = data.toList
    val interval: Int = (d.length / nSamples.asInstanceOf[Int]) match {
      case 0 => 1
      case x => x
    }

    def f(l: List[(Any, Any)], nSamples: Long): Unit = {
      if (nSamples > 0) l match {
        case _ if (nSamples == 0)  =>
        case Nil =>
        case List(h, _*) => 
          writer(h._1, h._2)
          f(l.drop(interval), nSamples - 1)
      }
    }

    f(d, nSamples)
  }
}

class SampleFactory extends AggregatorFactory {
  override def createNew(keyType: SerializedType,
                valType: SerializedType,
                args: List[Long]): Aggregator = new Sample(args(0))

  override def check(keyType: SerializedType,
            valType: SerializedType,
            args: List[SerializedType], 
            options: Map[String, SerializedType]): Option[List[String]]= {

    val aggrName = "sample"

    val argsErrors = checkNumOfArgs(aggrName, args.length, 1) match {
      case Nil if (args(0) != Int64Type) => List("First arguments must be int type")
      case x => x
    }

    val optionErrors = checkOptionName(aggrName, options, List()) 

    (argsErrors ++ optionErrors) match {
      case Nil => None
      case x   => Some(x)
    }
  }
}
